Sediment ‘rings’ suggest rapid climate change

When geologists split open split core samples extracted from an area once covered by the ocean. they saw distinct clay bands about 2 centimeters thick that could only have been made by climate. “When we see cycles in cores, we see a process,” says Morgan Schaller. “In this case, it’s like a tree ring. It’s giving us a yearly account through the sediments.” (Credit: Gary Knight/Flickr, font by Vernon Adams)

A climate shift that happened 55 million years ago occurred over a period of weeks and months—not 10,000 years as previously believed—say scientists.

“Rapid” and “instantaneous” are words geologists don’t use very often. But geologists contend that following a doubling in carbon dioxide levels, the surface of the ocean turned acidic and global temperatures rose by 5 degrees centigrade—all in the space of about 13 years.

“We’ve shown unequivocally what happens when CO2 increases dramatically—as it is now, and as it did 55 million years ago,” says James Wright, professor of earth said planetary sciences at Rutgers.

“The oceans become acidic and the world warms up dramatically. Our current carbon release has been going on for about 150 years, and because the rate is relatively slow, about half the CO2 has been absorbed by the oceans and forests, causing some popular confusion about the warming effects of CO2.

“But 55 million years ago, a much larger amount of carbon was all released nearly instantaneously, so the effects are much clearer.”

Like a tree ring

The window to this important decade in the very distant past opened when Wright helped a colleague, Kenneth Miller, and his graduate students split core samples they extracted from a part of southern New Jersey once covered by the ocean.

The patterns found in the long cylinder of sediment told a story. There were distinct clay bands about 2 centimeters thick occurring rhythmically throughout the cores.

A close-up of the core. Note the regular dark bands–”like a tree ring,” Morgan Schaller says. (Credit: James Wright, Rutgers)

“They called me over and said, ‘Look at this,'” says Morgan Schaller, a research associate. “What jumped out at me were these rhythmic clay layers, very cyclic. I thought, ‘Wow, these have got to mean something.'”

The researchers surmised that only climate could account for the rhythmic pattern they saw. “When we see cycles in cores, we see a process,” Schaller says. “In this case, it’s like a tree ring. It’s giving us a yearly account through the sediments.”

This discovery provided the necessary data to finally solve the huge conundrum surrounding this event—the significant error in how fast the carbon was released.

Whatever the cause of the carbon release—some scientists theorize that a comet struck the earth—Wright and Schaller’s contention that it happened so rapidly is radically different from conventional thinking, and bound to be a source of controversy, Schaller believes.

“Scientists have been using this event from 55 million years ago to build models about what’s going on now,” Schaller says.

“But they’ve been assuming it took something like 10,000 years to release that carbon, which we’ve shown is not the case. We now have a very precise record through the carbon release that can be used to fix those models.”